<template>
  <div class="heart-wrap" :style="{ transform: `scale(${resultSize})` }">
    <div class="heart-inner">
      <div class="text-wrap">
        <span :style="{ color: textColor, 'font-size': `${resultFontSize}px` }">
          {{ text }}
        </span>
      </div>
      <div class="heart-canvas-wrap">
        <canvas id="pinkboard" ref="pinkboard"></canvas>
      </div>
    </div>
  </div>
</template>

<script setup>
import { onMounted, ref, watch, reactive, computed } from 'vue';

const props = defineProps({
  text: {
    type: String,
    default: 'LOVE'
  },
  textSize: {
    type: Number,
    default: 20
  },
  size: {
    type: Number,
    default: 500
  },
  textColor: {
    type: String,
    default: '#ea80b0'
  },
  heartColor: {
    type: String,
    default: '#ea80b0'
  },
  config: {
    type: Object,
    default: () => ({
      length: 300, // 数量
      duration: 2, // 粒子持续时间(秒)
      velocity: 100, // 移动是速度
      effect: -0.75, // play with this for a nice effect
      size: 30 // 单个 桃心 的大小
    })
  }
});

const resultSize = computed(() => props.size / 500);
const resultFontSize = computed(() => props.textSize / resultSize.value);

const pinkboard = ref(null);
let canvasEl;

onMounted(() => {
  canvasEl = pinkboard.value;
  puttingItAll(canvasEl);
});

watch(
  () => props.heartColor,
  () => {
    puttingItAll(canvasEl, props.heartColor);
  }
);

function getRndInteger(min, max) {
  return Math.floor(Math.random() * (max - min + 1)) + min;
}

/*
 * RequestAnimationFrame polyfill by Erik Möller
 */
(function () {
  var b = 0;
  var c = ['ms', 'moz', 'webkit', 'o'];
  for (var a = 0; a < c.length && !window.requestAnimationFrame; ++a) {
    window.requestAnimationFrame = window[c[a] + 'RequestAnimationFrame'];
    window.cancelAnimationFrame = window[c[a] + 'CancelAnimationFrame'] || window[c[a] + 'CancelRequestAnimationFrame'];
  }
  if (!window.requestAnimationFrame) {
    window.requestAnimationFrame = function (h, e) {
      var d = new Date().getTime();
      var f = Math.max(0, 16 - (d - b));
      var g = window.setTimeout(function () {
        h(d + f);
      }, f);
      b = d + f;
      return g;
    };
  }
  if (!window.cancelAnimationFrame) {
    window.cancelAnimationFrame = function (d) {
      clearTimeout(d);
    };
  }
})();

/*
 * Point class
 */
var Point = (function () {
  function Point(x, y) {
    this.x = typeof x !== 'undefined' ? x : 0;
    this.y = typeof y !== 'undefined' ? y : 0;
  }

  Point.prototype.clone = function () {
    return new Point(this.x, this.y);
  };
  Point.prototype.length = function (length) {
    if (typeof length == 'undefined') return Math.sqrt(this.x * this.x + this.y * this.y);
    this.normalize();
    this.x *= length;
    this.y *= length;
    return this;
  };
  Point.prototype.normalize = function () {
    var length = this.length();
    this.x /= length;
    this.y /= length;
    return this;
  };
  return Point;
})();

/*
 * Particle class
 */
var Particle = (function () {
  function Particle() {
    this.position = new Point();
    this.velocity = new Point();
    this.acceleration = new Point();
    this.age = 0;
  }

  Particle.prototype.initialize = function (x, y, dx, dy) {
    this.position.x = x;
    this.position.y = y;
    this.velocity.x = dx;
    this.velocity.y = dy;
    this.acceleration.x = dx * props.config.effect;
    this.acceleration.y = dy * props.config.effect;
    this.age = 0;
  };
  Particle.prototype.update = function (deltaTime) {
    this.position.x += this.velocity.x * deltaTime;
    this.position.y += this.velocity.y * deltaTime;
    this.velocity.x += this.acceleration.x * deltaTime;
    this.velocity.y += this.acceleration.y * deltaTime;
    this.age += deltaTime;
  };
  Particle.prototype.draw = function (context, image) {
    function ease(t) {
      return --t * t * t + 1;
    }

    var size = image.width * ease(this.age / props.config.duration);
    context.globalAlpha = 1 - this.age / props.config.duration;
    context.drawImage(image, this.position.x - size / 2, this.position.y - size / 2, size, size);
  };
  return Particle;
})();

/*
 * ParticlePool class
 */

var ParticlePool = (function () {
  var particles,
    firstActive = 0,
    firstFree = 0,
    duration = props.config.duration;

  function ParticlePool(length) {
    // create and populate particle pool
    particles = new Array(length);
    for (var i = 0; i < particles.length; i++) particles[i] = new Particle();
  }

  ParticlePool.prototype.add = function (x, y, dx, dy) {
    particles[firstFree].initialize(x, y, dx, dy);

    // handle circular queue
    firstFree++;
    if (firstFree == particles.length) firstFree = 0;
    if (firstActive == firstFree) firstActive++;
    if (firstActive == particles.length) firstActive = 0;
  };
  ParticlePool.prototype.update = function (deltaTime) {
    let i;

    // update active particles
    if (firstActive < firstFree) {
      for (i = firstActive; i < firstFree; i++) particles[i].update(deltaTime);
    }
    if (firstFree < firstActive) {
      for (i = firstActive; i < particles.length; i++) particles[i].update(deltaTime);
      for (i = 0; i < firstFree; i++) particles[i].update(deltaTime);
    }

    // remove inactive particles
    while (particles[firstActive].age >= duration && firstActive != firstFree) {
      firstActive++;
      if (firstActive == particles.length) firstActive = 0;
    }
  };
  ParticlePool.prototype.draw = function (context, image) {
    let i;
    // draw active particles
    if (firstActive < firstFree) {
      for (i = firstActive; i < firstFree; i++) particles[i].draw(context, image);
    }
    if (firstFree < firstActive) {
      for (i = firstActive; i < particles.length; i++) particles[i].draw(context, image);
      for (i = 0; i < firstFree; i++) particles[i].draw(context, image);
    }
  };
  return ParticlePool;
})();

/*
 * Putting it all together
 */
function puttingItAll(canvas, heartColor) {
  var context = canvas.getContext('2d'),
    particles = new ParticlePool(props.config.length),
    particleRate = props.config.length / props.config.duration, // particles/sec
    time;

  // get point on heart with -PI <= t <= PI
  function pointOnHeart(t) {
    return new Point(160 * Math.pow(Math.sin(t), 3), 130 * Math.cos(t) - 50 * Math.cos(2 * t) - 20 * Math.cos(3 * t) - 10 * Math.cos(4 * t) + 25);
  }

  // creating the particle image using a dummy canvas
  var image = (function () {
    var canvas = document.createElement('canvas'),
      context = canvas.getContext('2d');
    canvas.width = props.config.size;
    canvas.height = props.config.size;

    // helper function to create the path
    function to(t) {
      var point = pointOnHeart(t);
      point.x = props.config.size / 2 + (point.x * props.config.size) / 350;
      point.y = props.config.size / 2 - (point.y * props.config.size) / 350;
      return point;
    }

    // create the path
    context.beginPath();
    var t = -Math.PI;
    var point = to(t);
    context.moveTo(point.x, point.y);
    while (t < Math.PI) {
      t += 0.01; // baby steps!
      point = to(t);
      context.lineTo(point.x, point.y);
    }
    context.closePath();
    // create the fill
    context.fillStyle = heartColor ? heartColor : props.heartColor;
    context.fill();
    // create the image
    var image = new Image();
    image.src = canvas.toDataURL();
    return image;
  })();

  // render that thing!
  function render() {
    // next animation frame
    requestAnimationFrame(render);

    // update time
    var newTime = new Date().getTime() / 1000,
      deltaTime = newTime - (time || newTime);
    time = newTime;

    // clear canvas
    context.clearRect(0, 0, canvas.width, canvas.height);

    // create new particles
    var amount = particleRate * deltaTime;
    for (var i = 0; i < amount; i++) {
      var pos = pointOnHeart(Math.PI - 2 * Math.PI * Math.random());
      var dir = pos.clone().length(props.config.velocity);
      particles.add(canvas.width / 2 + pos.x, canvas.height / 2 - pos.y, dir.x, -dir.y);
    }

    // update and draw particles
    particles.update(deltaTime);
    particles.draw(context, image);
  }

  // handle (re-)sizing of the canvas
  function onResize() {
    canvas.width = canvas.clientWidth;
    canvas.height = canvas.clientHeight;
  }

  window.onresize = onResize;

  // delay rendering bootstrap
  setTimeout(function () {
    onResize();
    render();
  }, 10);
}
</script>

<style lang="scss" scoped>
.heart-wrap {
  width: 500px;
  height: 500px;
  .heart-inner {
    width: 500px;
    height: 500px;
    position: relative;
    .text-wrap {
      width: 100%;
      height: 100%;
      display: flex;
      align-items: center;
      justify-content: center;
    }
    .heart-canvas-wrap {
      position: absolute;
      top: 0;
      left: 0;
      width: 500px;
      height: 500px;
      canvas {
        position: absolute;
        width: 100%;
        height: 100%;
        top: 0;
        left: 0;
      }
    }
  }
}
</style>
